Transporting slabs of dense material presents particular challenges given the weight, size, and potential for breakage of hard material configured as a slab. A variety of devices are available to assist in handling and transporting large slabs of marble, granite, glass, or otherwise flat, hard, and heavy objects. A stone slab may be transported between cutting area, finishing area, staging area and worksite using devices such as a wheeled cart or like means. Unique problems arise however in handling stone slabs due to their sheer size and weight. The large and unwieldy nature of a typical slab gives rise to additional problems during maneuvers such as ascending inclines, negotiating corners and the like.
Stone slabs must be supported in an upright position during transport in order to prevent breakage and to allow a proper fit through restricted spaces such as doorways, narrow hallways, and the like. In addition, breakage is more likely when a slab is carried flat not only due to increased probability of contact with obstacles but because of the inherent weakness of a slab in the cross sectional direction. Although the upright position is most suitable for slab transport, the slightest tipping or urging in a lateral direction must be avoided. The slab's great weight will carry it over quickly during a fall.
Consequently, it is difficult to find suitable means for supporting a slab in an upright position during rolling and for maintaining upright stability when obstacles and the like are encountered. Upright instability can be attributed in part to the limitations posed on the placement of the center of gravity for the cart due to the position of the wheel axles for the cart. The placement of cart wheel axles in particular limit the placement of the slab to a position above the wheel axles. Placement of the wheel axles prevents the lowering of the center of gravity and limits the stability of the cart regardless of the size of the wheels.
Prior art stone carts exist that assist in dealing with the sheer weight of a stone slab. Maneuvering the stone slab over worksite obstacles while maintaining upright stability may still be problematic for prior art carts. Some prior art stone carts, in order to handle the sheer weight of the heaviest slab likely to be encountered are typically constructed with small diameter metal wheels. Metal wheels, impressed with the weight of a large slab, are a problem however when rolling across finished floors or carpets. Such hard wheels combined with slab weight often leave marks or cause actual physical damage. Other prior art carts are limited by their fixed physical configuration which arises in an effort to accommodate slabs of different sizes.
One such prior art device is disclosed in U.S. Pat. No. 3,580,601 issued to Miles. The disclosed skate device allows for the transport of large objects but has characteristic disadvantages associated with devices of this and like kind. Because of the fixed length of the skate, longer objects placed upon the skate contact the surface of an incline before the first wheel of the skate. Such a situation gives rise to the potential for damage to slab corners and may prevent successful negotiation of the incline all together.
Attempting to accommodate all object sizes is problematic however for a device such as that disclosed in Miles which purports to be a multi-purpose device. Since objects of many sizes must be accommodated, a single average length must be used for the skate construction. A skate optimized for longer objects would be inefficient for handling shorter objects and vice versa.
In addition to the disadvantages already mentioned, other disadvantages are known to those skilled in the art. For example, although rubber tires are disclosed in Miles as a replacement for aluminum or resin rollers, they are nevertheless disadvantageous in that they are of a solid rubber construction. Solid rubber tires are known in the art to present many of the same disadvantages as metal rollers in terms of leaving marks or causing actual physical damage as described above especially when more delicate surfaces are encountered.